Stephen Slocombe and colleagues at the Scottish Association for Marine Sciences (SAMS) screened 175 microalgae species to find the best biofuel candidates (there are roughly 44,000 species of microalgae described). The goal of their study, published in Nature Scientific Reports, was to identify strains that could be grown on a large scale, at low cost, to produce biofuel. According to Slocombe, "while there is a lot of work being done on microalgae biotechnology - currently around 10,000 researchers across the world - no one has identified a shortlist of the best performing strains and how their properties could be used".
The study consisted of two screens. In the primary screen, they identified species that could be easily grown in bulk. After all, if you want a lot of biofuel, you need a lot of algae. In the secondary screen, the SAMS team identified those species that produced the most oil.
The screen returned two promising candidates, Nannochloropsis oceanica and Chlorella vulgaris. Species in the genus Nannochloropsis grow as non-motile spheres. They cannot be distinguished by microscopy, so are classified based on genetic features. In fact, Nannochloropsis is currently used as an additive in fish and human foods.
Like Nannochloropsis, species in the genus Chlorella are non-motile spheres. During the aftermath of World War II, the United States recognized the potential for algae such as Chlorella to serve as a low cost, high yield food source (Soylent Green is...algae).
Sound like science fiction? It's not. Two companies, Algae.Tec and Solazyme, are actively producing fuel and other products from microalgae on a commercial scale (see video). There's a good chance Nannochloropsis and Chlorella will help these companies get the most bang for their buck.
Sources: www.phys.org, Algae.Tec, Solazyme, Scientific Reports 5, article number: 9844 doi: 10.1038/srep09844, Wikipedia